Previously, epoxy resins have been used for sealing material and die bonding material (that is, adhesives to adhere dies such as LED devices and a base material such as a package) of LED devices. When the resin is too soft, particularly in die bonding material, there arises a problem of failing to bond in a wire bonding step performed after the die bonding step. Accordingly, epoxy resins, which are adhesive with high hardness, have been previously used for the die bonding material. The sealing material and die bonding material composed of epoxy resin is sometimes yellowed by strong ultraviolet and are liable to absorb light. Accordingly, they have a problem of durability such as lowering brightness of LED when used for blue LED or white LED.
Recently, demands for durability of LED has been increased, and epoxy resin has been substituted by silicones resin, which has excellent durability, for sealing materials of LED devices. As same as the sealing material, the die bonding material is required to have durability, and die bonding compositions composed of silicone resin material has been proposed (Patent Document 1). These compositions, however, do not always give cured products through heat curing to fulfill the sufficient hardness, and sometimes fail to perform constant bonding.